(a) Field of the Invention
The present invention relates to a tilting device to be provided on a frame, stand or the like holding a surgical microscope.
(b) Description of the Prior Art
Recently, with a considerable progress of medicine, a new remarkable operation and its manipulation technique have been developed and, also in the field of microsurgery in which a microsurgical operation is performed while being observed through a microscope for enlargement, the demand for surgical microscopes with a higher degree of performance has been increased with the progress mentioned above.
In surgical operations on cerebral in particular, it is strongly demanded to position smoothly and easily the surgical microscope and therefore time necessary for the changes of an observation angle which will often be performed during the operations needs to be shortened as far as possible. That is, the surgical microscope has to be supported to a stand or a ceiling suspension holder so that it can be moved rapidly and accurately into a desired position within a working space and fixed at the desired position, without any obstruction to the operation.
Further, it is often seen of late that a photographing devce is attached to the microscope to record various symptoms of patient and a TV camera is mounted on the microscope for the education of surgeons and nurses. As a result, the surgical microscope increases in weight and requires an arm and base to compensate the weight, holding the operability mentioned above.
In order to satisfy these requirements, for example, U.S. Pat. Nos. 3,762,796 and 3,762,797 disclose a position adjustable stand device comprising a link mechanism held to a fixed support through a three-axis full Cardan link mechanism allowing its freely combined rotational movement about three axes perpendicular to each other by means of a handgrip to attach anoptical observation instrument to the member at the end portion of the link mechanism capable of freely changing an angular position within a three-dimensional space. With the three axis full Cardan link mechanism used in this device, however, it is essential that the microscope is supported in such a way that the optical observation instrument or microscope (preferably its center of gravity) lies at the intersection of the three rotational axes perpendicular to each other. For this reason, not only each arm constructing the three-axis full Cardan link mechanism becomes complicated in shape and expensive, but also the entire stand device becomes large-sized due to the arrangement of the Cardan arm adjacent to the microscope and consequently the space to be freely utilized in operation is considerably limited. Also, each rotational axis is balanced by a balance weight, so that the balance weight has the same weight as in the microscope and the inertia force of the entire device produced when the microscope is moved will remarkably be increased. Therefore, the above device has the disadvantage that it is very difficult to stop rapidly and securely, at a desired position, the microscope which has once been moved.
In order to further satisfy the requirements stated above, a device is known, as disclosed in, for example, German Patent Laid-Open No. 3444313, that a tension coil spring whose one end portion is fixed to a disc rotatable with an arm supporting the microscope is movably mounted in a radial direction at the other end portion and rotation moment according to gravity acting on the microscope at various setting positions of the microscope is balanced with the tension of the coil spring so that the movement and stop of the microscope can smoothly be carried out. This device, however, has the defect that it is unsuitable for the support of the surgical microscope since the movement of the microscope is limited two dimensions.